Effects of Lygus lineolaris nymph feeding on anatomy of cotton squares in relation to EPG-monitored feeding
1 Eeva Sharma, 3 Felix Cervantes , 2 Elaine Backus and 1 John Bushoven,
1Department of Plant Sciences, California State University, Fresno, CA
2 USDA Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, Parlier, CA
3Department of Entomology, University of California, Davis, CA
Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae) is considered the most important insect pest affecting cotton, Gossypium spp., in the US, especially in the eastern and mid-southern states. Nearly 45.5% of U.S. acres of cotton were infested by Lygus spp. in 2012, with an individual lygus bug potentially capable of destroying up to 23,400 cotton squares per hectare. Both immature and adult stages cause significant economic damage to cotton. However, fifth instar nymphs are more damaging than third instar nymphs and adults. The objective of this research was to better understand the cause of nymphal lygus damage by identifying internal anatomical changes to cotton squares over a regular timecourse after standardized probing by L. lineolaris fifth instars, as quantified by electropenetrography (EPG). In this experiment, a standardized four hours of L. lineolaris probing was repeatedly applied to multiple cotton squares. The samples were held for varying time periods of 0, 4, 12, and 24 hrs. The tissue samples were then prepared for light microscopy to examine anatomical changes. Some of the changes observed in the plant tissue caused by lygus feeding were plasmolysis, cell disintegration, and discoloration of the tissues. There are also anatomical differences noticed among the various timecourse treatments.
